This invention relates to an improved jet dyeing apparatus for dyeing textile materials which is particularly desirable for use in dyeing textile fabrics in rope form. In apparatuses of this type, the fabric to be treated is continuously circulated through a treatment zone or transport tube in which dye liquor is applied to the fabric under pressure. The pressurized liquor serves a dual function, namely to dye the fabric as well as to impart movement to the fabric rope which is conveyed from the transport tube into a fabric storage chamber. Within the storage chamber, the fabric is submerged in excess dye liquor and moves through this chamber suspended in the liquor until it is removed from the opposite end for conveyance through the transport tube whereupon the cycle is repeated.
As noted, pressurized dye liquor is applied to the fabric in the fabric transport tube. For this purpose, the tube typically includes at least one peripheral liquor sprayer or "P.L.S." which is designed to apply the liquor under pressure to the fabric about its complete circumference. It is particularly desirable to apply the pressurized liquor in a way which enhances the interchange between the dyestuffs and the fabric in order to enhance the uniformity of the dye application to the fabric. In order to dye the fabric successfully, however, it is also necessary that the fabric travel at relatively high speeds through the transport tube, but while still ensuring that the desired level of liquor-fabric interchange occurs.
In order to increase operating speeds, it is customary to utilize relatively high liquor pressures in the peripheral liquor sprayer, for example, in order to enhance fabric throughput and fabric-liquor interchange. Unfortunately, the use of high water pressures often results in damage to the surface of the fabric (i.e., peeling or pitting) and "stitch" deformation. The problem is particularly acute with lightweight fabrics which are more susceptible to damage from the relatively high pressures which means that the fabric finisher must typically either reduce his operating rates or compromise the quality of the resulting dyed products.
Representative jet dyeing machines for dyeing fabrics in continuous rope form are shown, for example, in U.S. Pat. Nos. 3,587,256 (Spara), 3,949,575 (Turner, et al.), 3,982,411 (Kreitz), 4,083,208 (Ekstroem), and 4,318,286 (Sturkey). The art-recognized problems of surface degradation in dye treatments, and with lightweight fabrics in particular, are described in Kreitz and Sturkey. For his part, Kreitz suggests that a plurality of nozzles be utilized of differing construction depending upon the type of fabric to be treated in the jet dyeing apparatus. This increases downtime since the apparatus must be modified each time the weight of the fabric to be treated in the jet dyeing apparatus is changed materially. As an alternative, Sturkey proposes the use of a modified j-box and an elongate liquor transport tube which has a steep upward incline in order to ensure, according to Sturkey, that the treated fabric will be conveyed through the transport tube with relatively reduced surface degradation. The problem in the Sturkey device, however, is that the use of a single liquor sprayer at the inlet in combination with the elongate tube, means that extremely high pressures must be used in order to maintain any reasonable throughput through the jet dyeing machine.
A still further modified jet dyeing apparatus is described in U.S. Pat. No. 4,083,208 to Ekstroem which also recognizes the problem presented by the desire to use the same jet dyeing apparatus for the purpose of dyeing either lightweight or heavier fabrics as well as yarns. Ekstroem suggests the use of a discharge pipe of varying undulated constructions which also requires changes in piping construction depending upon the weight of the fabric to be treated. Furthermore, Ekstroem advocates the use of a perforated region in the undulated pipe for the purpose of reducing the rate of travel in the fabric, ostensibly for the reason of reducing turbulence at the discharge point, but with the result that substantial liquor will be drained from the fabric while it is still in the transport chamber, and with the additional result that the capacity of the apparatus will be unduly restricted.
Additional fabric transporting arrangements are shown in U.S. Pat. Nos. 1,665,624 (Conrad), 2,228,050 (Collier), 2,403,311 (Steele), 3,802,840 (Chiba, et al.), 4,041,559 (Von Der Eltz), 4,142,385 (Sandberg, et al.), 4,766,743 (Biancalani, et al.), and in United Kingdom patent application 2,031,969, French publication no. 2,315,564, and German Offenlegungschrifft 2,140,788 which depicts an apparatus for loading and unloading textile material to be wet treated.
Even where higher throughput rates in the fabric transport tube are achieved, related problems can arise which limit the effective capacity of the jet dyeing apparatus. Specifically, it is customary in dyeing fabrics that the fabric leaving the fabric transport tube is delivered into the storage chamber, which is otherwise referred to as the "j-box" or keir. The apparatus which controls the placement of the fabric within the storage chamber or j-box is typically referred to as the "plaiter". It is customary in plaiting the fabrics to induce the formation of longitudinal folds in the fabric as shown, for example, in U.S. Pat. Nos. 4,318,286 (Sturkey) and in 4,023,385 (Hurd), the latter of which describes an oscillating valve for inducing formation of the folds through the use of air pressure. These arrangements can create problems in the form of entanglement of the fabric in the chamber and are inefficient because the capacity in the storage chamber is under-utilized.
Alternative arrangements for plaiting fabrics in a jet dyeing machine are shown in U.S. Pat. No. 2,579,563 to Gallinger and in United Kingdom patent application 2,004,927 ("Mezzera"). In accordance with the disclosures in these additional references, a plaiting nozzle is oscillated transverse to the direction of travel of the fabric through the fabric transport tube and is also preferably oscillated in a longitudinal direction (using the hood 21 in Mezzera, for example) or by axial movements of the discharge nozzle in accordance with the embodiment shown in FIG. 4 of Mezzera. The transverse and longitudinal action results in a parallelepiped arrangement of the fabric which is said to improve the stability of the stored fabric in the j-box in order to attempt to minimize occurrences of fabric entanglement within the j-box or storage chamber.
A similar problem of the instability of the fabric leading to entanglement also arises from the use of a fabric discharge nozzle of the orientation shown in the Mezzera United Kingdom reference described above since the angle of the discharge nozzle is disposed outwardly in a manner which will inherently deposit the fabric in a generally arcuate pattern as it is placed in the j-box. This stack is inherently unstable and wastes capacity within the storage chamber. Here again, the most significant problems are presented by lightweight fabrics and, as noted above, it is particularly desirable to provide a jet dyeing apparatus which is effective for dyeing both lightweight as well as heavier weight fabrics while maximizing the overall capacity of the apparatus.
It is also desirable in connection with the jet dyeing of fabrics to provide an effective means for rinsing unwanted impurities from the treated textile materials after wet processing in order to obtain optimum results The easiest way to obtain acceptable results is to rinse at a high liquor to goods ratio with many changes in fresh liquor The time associated with draining and then filling the apparatus, however, greatly increases the total cycle time required to complete the dyeing process. Furthermore, the increasing costs associated with water use and related waste water treatment, has created a need for rinsing techniques and apparatuses which are effective at reduced overall water consumption while still providing an efficient and effective rinse cycle.
An added complication arises from the fact that in many cases it is considered undesirable to drain the liquor completely in the first rinsing stage (i e., "drop fill rinsing"). For example, in the exhaust dyeing of cellulosic fibers with sulfur dyes, the dye is exhausted onto the fibers from a strongly reducing alkaline liquor Subsequently the dye is oxidized on the fiber to render the dye insoluble in water. In order to prevent localized premature oxidation, the reduction potential of the liquor and the concentration of alkaline must be reduced gradually and evenly as the dye concentration is reduced The use of drop fill rinsing can cause "bronzing" as a result of the migration of dye to the surface and oxidation on the fiber surface instead of within the interstices of the fiber structure Therefore, a technique known as "overflow rinsing" must be utilized in connection with this and other dyeing techniques. Unfortunately, overflow rinsing involving the introduction of large volumes of fresh water is also inefficient in terms of water consumption and time.
The problems associated with the prior art dyeing apparatuses in terms of increasing throughout and improving the quality of the resulting dyed fabrics have been largely overcome by the apparatus and method disclosed in prior European Application No. 91909184.3 (U.S. Pat. No. 5,299,339), the disclosure of which is incorporated herein by reference. In accordance with the teachings of this patent, an improved jet dyeing apparatus is provided which includes a plurality of peripheral liquor sprayers and a preferred design for a liquid transport tube which improves dyeing efficiency. In addition, a unique plaiter design is also disclosed which reduces instances of fabric entanglement in the jet dyeing apparatus. Despite the substantial improvements in efficiency and quality which may be achieved through the use of this apparatus, the need remains for an apparatus and method which provides suitable rinsing efficiencies while at the same time reducing the overall time required to complete the dyeing process.